Senile dementia, also known as Alzheimer's disease, affects a number of people around the world in spite of races, sex, etc. In view of the current situation that the aging population is on the sharp increase, senile dementia poses one of the serious health problems in the 21st century. Presently, there are presumably more than 300,000 patients suffering from senile and vascular dementia in Korea.
In the case of western countries, Alzheimer's disease is known to be present in about 10 percent of those over 65 years old and in about 40 to 50 percent of those over 80 years old. In addition, the number of patients suffering from Alzheimer's disease has been growing over time in Japan and China.
Although a number of theories recently have been proposed concerning the cause of Alzheimer's disease, such as viral infections, toxic poisoning by aluminum and amyloid beta-protein deposited on neuronal cells, the cause of this disease is not obvious.
Therefore, causative therapy cannot be applied due to the unknown pathogenesis of Alzheimer's disease. However, since the most noticeable characteristics in dementia patients are the reduction of chlolinergic functions in the central nervous system, many researchers have tried to improve the symptoms of Alzheimer's disease, through the enhancement of the level of acetylcholine in the brain by administering an acethylcholine precursor, cholinergic agonist or acetylcholinesterase inhibitor (hereinafter called "AChEI").
As a result of intensive endeavors in research, some drugs, such as SDZ ENA 71 (carbamates and a series of miotone derivatives) or L-Huperzine A, were developed, but they have yet to exhibit satisfactory anti-dementia effects. Furthermore, the development of AChEI specific to the CNS is still in the infant stage.
The currently available anti-dementia agents around the world include the following: i) AChEI drugs for improving the symptoms of cognitive deficits through the elevation of acetylcholine level, ii) metabolic drugs increasing the energy metabolism of neurons nonspecifically, and iii) blood-circulation enhancer improving the circulation of micro-blood. However, the effects of these drugs are temporal and marginal, and there is no report that these drugs were useful as a remedy for Alzheimer's disease patients. Further, the side-effects of conventional drugs, due to the stimulation of parasympathetic nerve cells, include nausea, vomiting and bronchoconstriction. Other side-effects, such as depression, insomnia, hypertension, and constipation, have been reported.
Therefore, there is an urgent need to develop an anti-dementia agent displaying a remarkable therapeutic efficacy for dementia, while improving cerebral pathological change with less adverse effects.